1. Field of the Invention
The present invention relates to sulfone derivatives useful in the fields of pharmaceuticals, food and feed additives, and to a process for producing the same.
2. Description of the Related Art
Heretofore, as processes for producing canthaxanthin derivatives and astaxanthin derivatives, a method is known in which a key intermediate, a specific C13 ketone (.beta.-ionone), is subjected to a carbon-increment reaction at its side chain to produce the target ccmpounds via Vitamin A and further .beta.-carotene (Pure Appl. Chem. (1991), 63(1), 35-44). However, .beta.-ionone, which is synthesized via multiple steps, is commercially rather expensive.